Mobile device screen or portion thereof with a graphical user interface



The FIGURE is a front view for a mobile device screen or portion thereof with a graphical user interface showing our new design.

The outermost broken lines show a mobile device screen or portion thereof. The other broken lines, including the slashed line text, show portions of the graphical user interface. None of the broken lines form part of the claimed design. 

CLAIM The ornamental design for a mobile device screen or portion thereof with a graphical user interface, as shown and described. 